1. Technical Field
Embodiments described herein are related to a system on a chip (SOC) including a secure processor and an always-on component.
2. Description of the Related Art
As the number of transistors that can be incorporated on a single semiconductor substrate “chip” continues to increase, the variety and complexity of functionality on the chip continues to increase as well. One way in which the available transistors can be used is to form an SOC. The SOC generally includes one or more processors and various other components (e.g. one or more memory controllers, various peripheral components, etc.).
Because SOCs incorporate significant functionality in a small form factor, and because SOCs can be made power efficient, SOCs are a popular device to include in mobile devices such a portable phones (cell phones), personal digital assistants (PDAs), smart phones that combine phone functionality and other computing functionality such as various PDA functionality and/or general application support, tablet computers, laptops, net tops, smart watches, wearable electronics, etc. These mobile devices have significant processing power and are increasingly being used for financial management and financial transactions, user communications other than voice (text, email, web browsing, etc.), streaming video, etc. Accordingly, SOCs may operate on private user data as well as data belonging to others (e.g. copyrighted audio, video, and still images). Accordingly, the security of the SOC and its ability to resist attacks meant to compromise secure data are becoming increasingly important features.
Many mobile devices may operate in a “standby” mode much of the time. In the standby mode, the device may appear to be “off,” in as much as the device is not actively displaying content for the user and/or not actively performing functionality for the user. In the standby mode, much of the device may indeed by powered off. However, in the background, the device may be listening for phone calls or network packets, checking for alarms, reacting to movement, etc.
Because the mobile devices are often operating from a limited supply (e.g. a battery), energy conservation is a key design consideration for the devices. In “standby” mode and other low power modes, it is desirable to power down the SOC to eliminate leakage current losses, which are a significant factor in energy consumption in modern integrated circuit technologies. On the other hand, the SOC is needed for some of the standby functionality mentioned above. Accordingly, the SOC (or portions thereof) may be powered up and powered down repeatedly during use, even though the overall mobile device is not completely off. This operation further complicates ensuring the security of the device as the SOC may be vulnerable to attack during power up/power down operations.